The present invention relates to an adaptable laser apparatus, for example capable of emitting a radiation able to have different wave lengths.
The laser apparatus according to the invention is more particularly, although not exclusively, intended for therapeutic applications, but other applications of said apparatus may be envisaged, such as for the treatment and machining of metallic pieces.
In its preferential application, the laser apparatus may emit a radiation having either a wave length of 1.06 micrometer, which is specifically appropriate for the coagulation and haemostasis of human tissues, or a wave length of 1.32 micrometer which is then specifically appropriate for surgery by vaporization of said tissues.
Laser apparatus are already known whose production makes it possible to emit a radiation able to have two specific wave lengths.
For example, document US-A-3 569 859 describes a laser apparatus comprising a plasma tube disposed in a resonant cavity constituted by two reflectors, of which one is totally reflecting, whilst the other is partially reflecting. The plasma tube containing a gas, such as for example carbon dioxide, is connected to a D.C. generator for exciting said gas. Furthermore, a displaceable element made of zinc sulfide may be disposed, coaxially, between the tube and the partially reflecting reflector, and is intended to act as filter.
Thus, when the zinc sulfide element is located outside said cavity, the wave length of the radiation emitted by the apparatus is of the order of 10.6 micrometers, whilst, when the zinc sulfide element is located in the cavity, between the partially reflecting reflector and the tube, the wave length of the radiation emitted by the apparatus is of the order of 9.6 micrometers, as part of the spectrum emitted is selectively absorbed by said filtering element.
Document PCT WO 86/03958 describes a laser apparatus intended for treatments of human tissues. The apparatus is of design substantially similar to that previously described, but comprises, instead of the displaceable filtering element made of zinc sulfide, a reservoir capable of containing a gas and disposed between the plasma tube and a partially reflecting mirror. In this way, when the vacuum is created, by means of a pump, in the reservoir, the wave length of the radiation emitted is of the order of 10.6 micrometers, whilst, when a gas, for example SF6, is injected in the reservoir by appropriate supply means, the wave length of the radiation emitted then corresponds substantially to 9.6 micrometers, the gas SF6 acting as filter for the radiation emitted by the tube.
Document EP-A-0 109 959 also discloses an apparatus of the YAG laser type, for therapeutic applications, and which comprises in particular, as active medium, a bar made of YAG, a reflecting mirror, a partially reflecting mirror and a controllable pivoting prism, disposed between the YAG bar and the reflecting mirror. The bar is connected in particular to a source of energy. This type of YAG laser apparatus is capable of emitting a radiation able to have at least two specific wave lengths, namely either 1.06 micrometer or 1.3 micrometer. Modification of the wave length of the radiation emitted is obtained by appropriate pivoting of the prism, actuated by a lever or the like. Thanks to the addition of an optical fiber to said apparatus, a practician can thus treat different human tissues by the appropriate use of one or the other of the specific wave lengths.
These apparatus, briefly described hereinabove, present in particular the drawback of providing elements supplementary to the laser system proper comprising an active medium and a resonant cavity, in order to allow, by their interposition in the path of the radiation emitted, the modification of the wave length thereof. This consequently brings about problems of alignment, particularly angular, of the reflectors of the resonant cavity with respect to one another, as well as between said reflectors and said active medium, always technically difficult to overcome.
Other laser apparatus capable of emitting a radiation of different wave lengths are also known, particularly by documents PCT WO 85/01445 and DE-2 809 007.
Each apparatus essentially comprises two independent laser sources, generally a YAG laser source and a CO.sup.2, laser source, which each emit a radiation of specific wave length. Via means for switching the two laser sources, the user may modify and choose the appropriate wave length of emission. However, these apparatus, since they use two independent laser sources, are expensive, cumbersome and nonetheless complicated, since it is necessary to provide means for aligning the radiations emitted by said sources.